, although the face centered cubic microstructure means that the transport of hydrogen is slower than in high strength steels, and hence the crack growth rate may be lower. The cracking is normally intergranular. As with steels the susceptibility becomes more severe as the strength of the alloy is increased. However, there is also a strong effect of heat treatment and microstructure, and quite high strengths can be obtained with good SCC resistance (as is demonstrated by the use of these alloys in aircraft construction). Any environments that can provide hydrogen can lead to SCC of susceptible alloys, ranging from humid air to salt solution. (reference)